In printing machines, the paper sheet stack is lifted gradually according to the sheets taken off by means of a lifting device to a loading head. The loading head takes off individual sheets of paper from the top level of the stack and moves them further, usually to a conveyer belt. The lifting device is usually provided with a board on which a stack of paper sheets is resting. The board is moved upwards by means of brackets that are lifted by a chain. The brackets are guided in guiding bars so as to keep the top surface of the stack at the working level of the loading head. In the past, it was necessary to stop the machine first and then to fill a new stack of paper sheets. Thereby, the printing process was regularly interrupted and a time loss was caused when a new paper sheet stack was being filled. This time loss was further increased in case of a repeated printing machine set-up at the printing process re-start. An improvement was brought by the device called NON-STOP loader. This loader allows refilling of a new paper sheet stack having a limited lower height. It is not necessary to interrupt the printing process of the printing machine and there are no time losses in printing orders of a large number of copies. Use of a NON-STOP loader is generally known and manufacturers of printing machines deliver it as a supplementary device to the loading device for take-off and transport of paper sheets into a printing machine.
Apart from the lifting device of the main paper sheet stack, the NON-STOP loader is usually provided with an auxiliary lifting device having an independent lifting chain, guiding elements and lifting elements. It makes possible to take over the lifting function of the main stack at a sufficient time reserve before the take-off of the last paper sheets from the main sheets stack; e.g. by putting a system of bars making a grillage under the remnant of the main stack. Without interrupting the sheets take-off at the top surface of the auxiliary stack, the board with the main stack can be moved down to the bottom level. The board is refilled again with a new paper sheet stack having a height, which is just below the bottom edge level of the lifting beam of the auxiliary stack of the NON-STOP loader. Thereafter, the board with a new main stack is lifted upwards. When it arrives to the top, under the upper auxiliary stack, it supports the grillage formed by bars from the bottom and takes over the lifting of the auxiliary stack After the supporting bars of the grillage have been removed, the board with the main stack continues in lifting of the whole stack. This stack is now composed of the remnant of the original stack, which is now the auxiliary one, and of a new main one, which is beneath.
The lifting device of the auxiliary stack is formed by a front beam and a rear beam that serve in supporting and lifting the bottom bars of the auxiliary stack. The bars are suspended on chains. Movement of the chains is synchronised for the front and the rear beams of the auxiliary stack. However, it is independent of the main stack lifting device chain movement. The guiding bars of the front beam and of the rear beam of the auxiliary stack are situated in front of the auxiliary stack and behind it, outside the plan of the main stack bearing board. Therefore, the guiding bars have to be fixed to the front side of the machine at the loading head. If the guiding bars are fixed directly on the machine frame on both sides, it is on the operator's side and the other side, then the machine frame reaches behind the verge of the main stack board. The guiding bars can be fixed also by means of a special structure, which is an integral part of the machine in the so equipped machines and reaches again behind the verge of the main stack board in the direction out of the machine. This placing of beams guiding exactly on the operator's side makes a free and barrier-free movement of an operator during paper loading and machine set-up impossible, and this even in spite of the fact that this rear beam of the NON-STOP loader is dismounted from the bearing chains suspensions when not in use. The prolonged machine frame is disadvantageous also because it limits movement of an operator both around the paper stack and around the loading head and above them.